TI Gray Alternate

MUX

LED_DRV1

LED_DRV2

TX8

TX7

TX6

TX5

TX4

TX3

TX2

TX1

1.8V LDO

ALDO_1V8,

DLDO_1V8

RX_SUP

LDO_BYP

INP1

INM1

INP2

INM2

INP3

INM3

INP4

INM4

INA

LPF

VCM

ECG_INP

ECG_INM

RLD

ADC

Lead

Detect

Bias

+

±

256-sample

FIFO

SPI, I2C

Timing Engine

128 kHz

Oscillator

4 MHz

Oscillator

Processing,

Decimation

Filters

ECG Lead,

Threshold

Detection

ECG Lead

detection

comparators

CLK

SPI, I2C

ADC_RDY

GPIO2

+

±

Rf1

Cf1

Rf1

Cf1

TIA1

AACM

Noise

Reduction

Filter

2 PPG RX Channels

TX_SUP

Product

Folder

Order

Now

Technical

Documents

Tools &

Software

Support &

Community

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. ADVANCE INFORMATION for pre-production products; subject to

change without notice.

AFE4950

SBASA37 – JUNE 2020

AFE4950 Ultra-Small, Integrated AFE for Wearable Optical Heart-Rate Monitoring, SpO2

and Electrical Bio-sensing

1

1 Features

1

•

Supports simultaneous & synchronized acquisition

of up to 24 PPG and a single-lead ECG signal.

•

Flexible allocation of 8 LED, 4 PD in each phase

•

ECG signal chain:

–

1-lead ECG signal acquisition up to 2 kHz

–

RLD output to drive a third electrode

–

Input noise : 0.7 µV-rms

–

Supports up to +/- 0.65 V differential DC offset

and +/-0.55 V common mode range

–

Programmable INA gain: 11, 21

–

High-pass filter with quick saturation recovery

–

Integrated 300 Hz anti-aliasing low pass filter

–

AC, DC lead-off detect: 3.125-nA to 100-nA

–

Low power continuous lead-on detection

•

Impedance signal chain

–

Continuous low-power monitoring of

impedance between 2 electrodes

–

7 MΩ range with 1 kΩ accuracy

•

PPG Transmitter:

–

8-Bit Programmable LED Current with range

adjustable from 25 mA to 250 mA

–

Mode to fire two LEDs in parallel

–

Support of 8 LEDs in Common Anode

configuration for SpO2, Multi-Wavelength HRM

•

PPG Receiver:

–

2 parallel receivers (two sets of TIA/ filter)

–

Supports 4 Time-Multiplexed Photodiode

Inputs to each Receiver

–

8-bit Ambient Offset subtraction at each TIA

input with 256 µA range

–

8-bit LED Offset Subtraction DAC with 64 µA

range

–

Automatic ambient cancellation and dynamic

LED DC cancellation at TIA input

–

Ambient rejection close to 100 dB up to 10 Hz

–

Noise filtering with programmable bandwidth

–

Trans-impedance Gain: 3.7 kΩ to 1 MΩ

•

Accurate, Continuous Heart-Rate Monitoring:

–

System SNR up to 109-dB at 16 µA PD

current

–

Low Current for Continuous Operation on a

Wearable Device with a Typical Value: 15-μA

for an LED, 20-μA for the Receiver

•

External clock and internal oscillator modes

•

Acquire data synchronized with system master

clock

•

FIFO with 256-sample Depth

•

•

2.6-mm × 2.5-mm DSBGA, 0.4-mm Pitch

•

Supplies: Rx:1.7-1.9V (LDO Bypass); 1.9-3.6V

(LDO Enabled), Tx:3-5.5V, IO:1.7-RX_SUP

2 Applications

•

Optical Heart-Rate Monitoring (HRM) for

Wearables, Hearables

•

High performance ECG signal acquisition

•

Synchronized PPG, ECG for BP estimation

•

Heart-rate variability (HRV)

•

3 Description

The AFE4950 device is an analog front-end (AFE) for

synchronized signal acquisition of PPG and ECG

signals. The device can also be used for optical bio-

sensing applications, such as heart-rate monitoring

(HRM) and saturation of peripheral capillary oxygen

(SpO2). The ECG signal chain supports 2- and 3-

electrode configurations and has an integrated Right

leg drive (RLD) buffer.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (NOM)

AFE4950

DSBGA (36)

2.60 mm × 2.50 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Simplified Schematic